FIX to display function handling null element reference, and wrong target parameter values (#1784)

* blacked

* More robust code for display, with tests

Display now includes more robust controls when checking
the input target parameters, with appropriate exception raised
(i.e. ValueError or TypeError) whether target is either
an empty string, or a not-string, not-None type, respectively.

The TypeError aligns with other similar behaviour with other Pyton
functions (e.g. str.split with integer separator).

Also, now display raises a ValueError whether the target element
is not found or not existing.

All changes are supported by tests.

* traceback lines in check_py_error & removed clones

check_py_error function now automatically includes
check of the traceback in console errors.

This way tests in basic and display have been refactored,
and lots of duplicated code removed.

* removed useless console check lines.

If check_py_errors function is running, those
console log lines are useless to check.

pyscript.core/tests/integration/test_01_basic.py

@@ -106,10 +106,6 @@ class TestBasic(PyScriptTest):
         assert "hello pyscript" in self.console.log.lines
         self.check_py_errors("Exception: this is an error")
         #
-        # check that we sent the traceback to the console
-        tb_lines = self.console.error.lines[-1].splitlines()
-        assert tb_lines[0] == "PythonError: Traceback (most recent call last):"
-        #
         # check that we show the traceback in the page. Note that here we
         # display the "raw" python traceback, without the "[pyexec] Python
         # exception:" line (which is useful in the console, but not for the
@@ -138,10 +134,6 @@ class TestBasic(PyScriptTest):
 
         self.check_py_errors("Exception: this is an error inside handler")
 
-        ## error in console
-        tb_lines = self.console.error.lines[-1].splitlines()
-        assert tb_lines[0] == "PythonError: Traceback (most recent call last):"
-
         ## error in DOM
         tb_lines = self.page.locator(".py-error").inner_text().splitlines()
         assert tb_lines[0] == "Traceback (most recent call last):"